1. Field of the Invention
Embodiments of the present invention generally relate to a magnetic read head for use in a hard disk drive, in particular, a magnetoresistive effect read head having a side shield.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads thereon, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to position the read and/or write heads over selected data tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The read head of a hard disk drive includes a spin valve element utilizing a magnetoresistive effect. By sensing the relative magnetizations of two ferromagnetic thin films sandwiching an intermediate layer, magnetic information can be read from nanoscale magnets on a recording medium. Reductions in various dimensions of the sensor element and improvements in the film characteristics have contributed to improvements in recording density, allowing current recording tracks to achieve a width less than approximately 100 nanometers. However, further improvements in recording density using previously known devices have proven to be difficult.
In response, one proposed solution to further increase recording density is the side shield read head. The side shield read head includes a soft magnetic body in the track width direction of the spin valve element, thus leading to sensitivity reduction at the skirt region of the read sensitivity distribution in the track width direction. The skirt reduction of the read sensitivity distribution occurs because the spin valve element captures the magnetic field generated at the center part of the recording track, and the magnetic shield formed by a soft magnetic body absorbs the magnetic field generated by portions of the recording track other than the center part. By reducing the skirt of the sensitivity distribution, the track density can be improved because the reading noise and interference of adjacent tracks can be reduced.
In previously known side shield read heads, adequate signal output cannot be obtained because of read utilization decreases, as explained with reference to FIGS. 1A and 1B. FIG. 1A is a partial perspective view of a magnetic head 100 having side shields 102 and a sensor element 103. FIG. 1B is a top view of the spin valve element 100 shown in FIG. 1A. When there is no magnetic field from the recording medium 106, the magnetization direction in the side shield 102 is horizontal; consequently, the magnetization direction of the soft bias magnetic field is also horizontal. As shown in FIG. 1B, when the side shield 102 absorbs a magnetic field 110 from the recording medium 106, the magnetization direction in the side shield 102 is tilted in the direction of the magnetic field 110, as shown by arrows 108. As a result, the soft bias magnetic field has a component in the element height direction, e.g., magnetic field 115. The magnetic field 115 acts to suppress tilting of the magnetization of a free layer in the sensor structure 103. As shown in FIG. 1B, the tilt angle from horizontal direction of the magnetization direction in a free layer, as shown by arrow 114, is smaller than that of the magnetization direction without the magnetic field 115, as shown by broken arrow 116. This results in a decrease of the read utilization of the read sensor.
When the read utilization decreases, the read output also decreases, and a high signal-to-noise ratio (SNR) cannot be obtained. If the gap between the free layer and the side shield widens, the bias strength decreases and the utilization improves, however, the effect of a sensitivity reduction in the skirt region of the read sensitivity distribution is hindered (and consequently, noise reduction is hindered).
Therefore, there is a need in the art for a read head with both higher read utilization and a sensitivity reduction in the skirt region of the read sensitivity distribution.